There are presently available industrial spray painting systems in which a turbo-compressor and its associated drive motor are mounted upon a cart so that the unit may be moved about within the plant to the article to be painted.
In units of this type, the motor and turbo-compressor typically are mounted side by side upon a horizontal plate which constitutes the top of the cart with the motor shaft and turbine shaft extending vertically downwardly through their housings and the mounting plate to be coupled to each other by a drive belt located below the mounting plate. Typically, a box-like chamber is provided at the underside of the mounting plate to enclose the shafts and drive belt which are driven at relatively high speed.
In the usual case, the turbo-compressors have multiple stages with the final stage being located at the bottom of the compressor. The chamber which encloses the final stage is defined in part by the bottom of the compressor housing, through which the drive shaft must project. Because of the high speed rotation of the drive shaft, the shaft bearing employed at this last location cannot tightly seal this opening, and in operation of the turbine there is a continuous and relatively high rate of flow of compressed air from the final stage chamber through what is effectively a relatively restricted orifice into the chamber below the mounting plate. This airflow generates a relatively high noise level, frequently in the range of 100 decibels. The chamber into which this air is discharged cannot be sealed because as the air is compressed during its passage through the turbo-compressor, its temperature is also elevated and it is necessary to induce a flow of air through the shaft and drive belt enclosing chamber to prevent an undesirable amount of heat buildup.
The present invention is especially directed to a noise suppressor especially adapted for use in the system described above.